function gy = biharmonic_gy(x,y,caseNum,varargin)
switch caseNum
    case 1
        gy = exp(x+y);
    case 2
        theta = (2*atan2(y+eps,x+eps)+pi)/3;
        r = (x.^2+y.^2+eps).^(-2/3);
        gy = 2*r.*(y.*sin(theta) + x.*cos(theta))/3;
    case 3
        t = 5*atan2(y+eps,x+eps)/2;
        r = sqrt((x.^2+y.^2));
        gy = 2.5*sqrt(r).*(y.*sin(t)+x.*cos(t));
    case 4
        gy = 4*y.^3;
    case 5
        gy = 3*cos(x+3*y);
    case 6
        gy = exp(2*x+y);
    case 7        
        gy = -1./((1+x+y).^2);
    otherwise
        gy = 0 * x;
end